Boston bombing suspect Tamerlan Tsarnaev made contact with two insurgents in Dagestan and considered joining a militant Islamist organization based in the Russian territory. But instead, he moved to the U.S. after both contacts were killed by Russian counterinsurgency agents.

As soon as the since-slain Tsarnaev, 26, was identified as a suspect in the Boston Marathon bombings, questions were raised as to how his Islamic views became increasingly radicalized. Most of this attention was placed on a six-month visit to Dagestan that Tsarnaev made last year.

Initial suspicion of Tsarnaev’s radicalization, based on information from Tsarnaev’s uncle Ruslan Tsarni, fell on a Rhode Island-based convert to Islam known to Tsarni as “Misha.” But Misha (real name Mikhail Allakhverdov) has yet to be connected to the Boston attacks or to terrorism in general. He also denied having any contact with Tsarnaev for three years, although he acknowledged knowing the suspect.

Now, according to Russian media outlet Novaya Gazeta, a stronger association has been made between Tsarnaev and Mahmud Mansur Nidal -- an 18-year-old insurgent and liaison for a Dagestan-based underground insurgency movement who also helped recruit new members for the group for attacks on Russia.

Nidal had been under investigation by Russia’s Center for Combating Extremism (CEPE) -- a division of Dagestan’s Interior Ministry -- for at least a year when he was seen with Tsarnaev, a CEPE source told Novaya Gazeta. The source said Nidal and Tsarnaev were observed together “on multiple occasions.”

Nidal was killed by Russian special forces on May 19.

“He agreed to surrender at first but then reneged when the women and children [with the insurgency] had been allowed to leave. Nidal knew that the special forces had too much information about him,” a witness to the surrender told Novaya Gazeta.

The CEPE started investigating Tsarnaev in April 2012, but no banned websites or suspicious contacts were found on his cellphone. But the counterinsurgency organization realized that Tsarnaev raised red flags a year earlier.

William Plotnikov, a 21-year-old Canadian citizen and native of Russia who converted to Islam, was detained by the FSB -- the successor to the KGB -- following a tip from the CEPE that Plotnikov had ties to insurgents in Dagestan.

While being interrogated by the FSB, Plotnikov handed over his Internet contacts, including Tsarnaev. The contacts were comprised of immigrants from the North Caucasus living in the United States or Canada.

Plotnikov and Tsarnaev allegedly communicated via the Islamic social network World Association of Muslim Youth. Tsarnaev linked WAMY to his YouTube page, which also contained Islamic extremist material.

The information led the FSB to warn the FBI about Tsarnaev, but the bureau said it did not find any information that indicated Tsarnaev was a threat or a potential terrorist. Plotnikov was eventually released by Russian special forces after they could not find any criminal ties and later killed in a July 14 battle with special forces in Dagestan.

“We began investigating Tsarnaev and placed him on record after his name came up in the [Plotnikov] investigation in Dagestan,” a CEPE official told Novaya Gazeta. “We pay special intention to foreign nationals or Russians who recently converted to Islam -- they are extremely ideological and psychologically vulnerable. They can be convinced to do anything, even a suicide bombing.”

Tsarnaev arrived in the Dagestani city of Makhachkala in January 2012 and stayed in the city to see his father and renew his Russian passport, according to Novaya Gazeta.

He left his father’s house in May 2012, after Nidal was killed, to live with other relatives, and was rarely seen in public, the paper reported.

Following the killing of Plotnikov, Russian special forces expected Tsarnaev to be in the area. They were told by Tsarnaev’s father that he left for the United States but didn’t believe him.

“First we searched for him in the [Dagestan] republic, checking passenger lists for foreign flights, trains and watched for him at bus terminals. Then we widened the search to the [Northern Caucasus] region,” a source told the Russian media outlet.

Upon learning that Tsarnaev was in the U.S., the FSB sent another request to the FBI as well as an inquiry to the CIA to check in on Tsarnaev. The requests were ignored, according to Novoya Gazeta.

The CEPE official said the agency determined that Tsarnaev planned on joining the insurgency, but abandoned those plans after the deaths of his contacts.

“It appears that Tamerlan Tsarnaev came to Dagestan aiming to join the insurgents but was unsuccessful. It’s a difficult process -- first you make contact with the liaison, then there’s a ‘quarantine’ period -- the insurgents check out each person before allowing them to join. After his contacts, Nidal and Plotnikov, were killed, Tsarnaev got cold feet and fled,” the source said.